Pressure responsive switch



May 14, 1968 ARP ET AL 3,383,484

PRESSURE RESPONSIVE SWITCH 2 Sheets-Sheet 1 Filed Oct 13, 1965 May 14,1968 J, m: ET AL 3,383,484

PRES SURE RESPONS IVE SWITCH Filed Oct. 13, 1965 2 Sheets-Sheei :2

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iwwk United States Patent 3,383,484 PRESSURE RESPONSIVE SWITCH Leon J.Arp, 1221 Marston, and James M. Varnum, 428 Ash, both of Ames, Iowa50010 Filed Oct. 13, 1965, Ser. No. 495,649 1 Claim. (Cl. 200-83)ABSTRACT OF THE DISCLOSURE A pressure responsive switch comprising apair of plates adapted to be locked together with a cavity formedtherein. A pair of separate electric contacts are mounted in one plate,with the contacts being part of a normally open electrical switch, whichswitch can be connected to for operating any electrically responsivemechanism. A diaphragm is also mounted in the cavity which is responsiveto a differential pressure on either side thereof. An opening is formedin the plate of the contacts to transmit, for example, the negativepressure of a person inhaling through the opening, and a positivepressure of a respirator system forcing air therethrough to the person.*On the side of the diaphragm facing the contacts, an electricallyconductive disc is mounted which disc is operable to simultaneouslyengage the contacts, thereby closing the switch circuit. On the oppositeside of the diaphragm, due to a series of holes formed in the otherplate, air under atmospheric pressure is admitted therein for forcingthe diaphragm and its disc against the contacts in response to anegative pressure on the disc side of the diaphragm. An electromagneticdevice is also mounted on the opposite plate which is operable to varythe sensitivity of the pressure responsive switch by magneticallyaffecting the disc. The cavity on the electromagnetic device side of thediaphragm has a screen interposed between the diaphragm and theelectromagnetic device to prevent the diaphragm from contacting thedevice, and for insuring air under atmospheric pressure on the entiresurface of the diaphragm 'at all times irrespective of its position.

It is an object of this invention to provide a diaphragmtype switchwherein the diaphragm is movably responsive to a pressure differentialinduced by the inspiration or expiration of the patient to effect aclosed electric circuit to actuate the respirator, and wherein furtherthe response of the diaphragm to said pressure differential iselectro-magnetically controllable, thereby varying the controlsensitivity of the switch.

Yet another object of this invention is to provide 'a diaphragm-typepressure sensitive switch wherein the diaphragm is movable between apair of positions effecting thereby an open or closed electric circuit,and further wherein the one side of the diaphragm exposed to atmosphericpressure is always substantially exposed thereto in both positions.

It is another object of this invention to provide a pressure sensitiveswitch capable of attaining the above designated objects which isextremely economical to manufacture, simple and rugged in structure, andeffective in operation.

These objects, and other features and advantages of this invention willbecome readily apparent upon reference to the following description,when taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic illustration of a specific embodiment of theinvention;

FIG. 2 is an exploded elevational view of the invention showing therelative position of the various parts, with certain parts thereof shownin sectional view;

3,383,484 Patented May 14, 1968 FIG. 3 is a bottom plan view of theupper housing;

FIG. 4 is a top plan view of the upper housing;

FIG. 5 is a sectional view taken along the line 5-5 in FIG. 4;

FIG. 6 is an enlarged, fragmentary sectional view of the invention, andshowing the diaphragm in two alternate positions;

FIG. 7 is a top plan view of the base plate;

FIG. 8 is a sectional view taken along the line 8-8 in FIG. 7;

FIG. 9 is a bottom plan view of the base plate;

FIG. 10 is a plan view of the diaphragm;

FIG. 11 is an enlanged sectional view taken along the line 11-11 in FIG.10;

FIG. 12 is a plan view of the wire screen.

Referring now to the drawings, a commercially 'available nose or facemask 10 (FIG. 1), adapted to fit a living creature, has two ports 11 and12 formed therein. Fluidly connected to port 11 is a conduit 13 which isfluidly communicable at the other end 14 with the 'atmosphere. A secondconduit 16, fluidly connected to the port 12 is fluidly communicablewith a respirator 17 at a discharge port 18 formed therein. The conduit16 (FIG. 1) branches off at 21 with a third conduit 22 which is fluidlyconnected to a tube 23 mounted in a pressure sensing device generallyindicated 'at 24. The pressure sensing device 24 is electricallyconnected by lines 25 and 25a to the circuitry of the respirator 17 orother device responsive to inspiration or expiration for purposeshereinafter described.

The base plate 26 of the pressure sensing device (FIGS. 2 and 8),constructed of a non-metallic material, has an aperture 27 (FIG. 8)formed in the center thereof which receives the tube 23, and which opensinto an inverted frustro-conical cavity 28 formed in the top of theplate 26 as illustrated in FIG. 8.

Two diametrically opposite, parallel holes 29 and 31 (FIG. 6) are formedin the plate 26 on each side of the opening 28. Stainless steel screws32 and 33, with their shank end-s 34 and 35 ground to a point, forpurposes hereinafter described, are threadably inserted through back-upnuts 37 and 38 and into the holes 29 and 31. The nuts 37 and 38 areprovided to lock and to position the screws 32 and 33 to enable the ends34 and 35 thereof to protrude into the opening 28 for a predetermineddistance. Fastened to the heads of the screws 32 and 33 are the wires 25and 25a (FIG. 1). In this arrangement the screw ends 34 and 35 are theopen contact-s of a normally open electric switch, closeable ashereinafter provided.

The base plate 26 is completed by 'a quartet of tapped holes 39 (FIG. 7)formed, one in each corner, therethrough.

The upper housing 36 (FIGS. 2 and 5) of the pressure sensing device,constructed of Plexiglas or like nonmetallic material, is provided withan aperture 41 formed centrally therein, and which opens into anintermediate, circular cavity 42 having a larger diameter. Theintermediate cavity 42 leads into a larger circular cavity 43 formed inthe housing 36 on the under side thereof as best illustrated in FIG. 5.A plurality of arcuately spaced openings 44 (FIG. 3) are bored throughthe housing 36 and extended into the peripheral area of the cavity 43 as'best seen in FIG. 3. Four holes 46 are axially drilled through thehousing 36, one in each corner, for

alignment with the holes 39 in the plate 24. Secured to the surface 47of the shoulder formed between the cavity 43 and the cavity 42 is a finemesh circular screen 48 (FIGS. 6 and 12) which has 'a diameter greaterthan that of the cavity 42. It is seen that the screen 48 completelycovers the cavity 42.

Four screws 49 (FIGS. 2 and 6) are provided to secure the plate 26 tothe housing 36 by insertion through the aligned holes 46 and 39. Whenthe plate 26 and housing 36 are secured together a chamber 50 consistingof the cavities 43 and 28 is created therein, with the cavity 42 influid communication therewith through the screen 48.

Between the plate 26 and the housing 36 (FIG. 6), and thereby dividingthe cavity 50 into two parts, is stretched a circular, silicone rubberdiaphragm 51, also shown in FIG. 10, which under normal conditionsbecause of its tautness assumes the position shown by the dotted linesin FIG. 6. Bonded to the center of the diaphragm 51 and on the sidethereof facing the screw ends 34 and 35 is a circular stainless steeldisc 52, best shown in FIG. 2.

An electromagnet 53 (FIG. 2) is mounted on the housing 36 with its core54 (FIG. inserted into the aperture 41. The magnet 53 may be varied asto the strength of its field relative to attracting the disc 52, bymeans of a potentiometer 56 electrically connected thereto.

In operation of the system, air under atmospheric conditions enters thepressure sensing device 24 by flowing through the openings 44 (FIG. 6)and into the portion of the chamber 50 located above the diaphragm 51 asshown in FIG. 6. 'On the nose mask side of the diaphragm 51, or in thelower portion of the chamber as seen in FIG. 6, atmospheric conditionsalso exist when the respirator 17 is not functioning.

In use, the mask is placed over the face of the patient. Uponinspiration by the patient, a negative pressure is created in theconduits 16 and 22, as both are closed off from the atmosphere. With anegative pressure in the cavity 50 below the diaphragm 51, the positiveatmospheric pressure on the top side of the diaphragm 51 forces thediaphragm 51 to the distended full line position shown in FIG. 6,wherein the disc 52 contacts the ends 34 and of the screws 32 and 33,thereby closing the electrical circuit leading to the respirator 17,which is thereby activated. The activated respirator 17 then forces aproper supply of fluid through the conduit 16 to the nose mask and thelungs of the patient, while at the same time transmitting fluid throughthe conduit 22 into the chamber below the diaphragm, thereby creating apositive pressure against the diaphragm 51. This positive pressureforces the diaphragm upwardly and away from the full line position asillustrated in FIG. 6, and thereby breaks the contact between the disc52 and the screw ends 34 and 35, thus opening the circuit anddeactivating the triggering section of the respirator 17.

The patient on exhaling forces fluid from the nose mask 10 throughpassage 13 to the atmosphere and at the same time into the pressuresensing device 24 via the passages leading thereto. This exhalationmaintains the positive pressure on the disc side of the diaphragmcreated therein by the activation of the respirator 17. For an instant,between the inspiration and the expiration of the patient the entiresystem will again be under atmospheric conditions as describedhereinabove. The patient again inhales and the above described sequenceis again set in motion.

The potentiometer 56 controlled electromagnet 53 is mounted on thepressure sensing device 24 to regulate the sensitivity of the diaphragm51. If the electromotive force is increased by changing the setting ofthe potentiometer 56, the magnetic force created by the magnet requiresa greater negative pressure on the disc side of the diaphragm 51 toovercome the force holding the disc away from contacting the screw ends3-4 and 35. Therefore it can readily be seen that the pressure sensingdevice 24 can be used in a respirator system for either an infant or anadult by merely regulating the potentiometer.

The screen 48 is so mounted to prevent the diaphragm 51 and accompanyingdisc 52 from being forced into the cavity 42 and against the core of theelectromagnet 54 during operation of the device 24. Atmospheric airentering the chamber 50 via the holes 44 can pass through the screen tobe on the top side of the diaphragm so as to act on substantially theentire surface thereof. If the screen was not so mounted, atmosphericair would only act on the annular peripheral portion of the diaphragm51. This could result in a disadvantageous sticking of the disc 52 tothe core 54 which would adversely eflect the operation of the device.

It can, of course, be visualized that the pressure sensing device couldbe connected to a signal device instead of a respirator, whereby achange in pressure would cause an alarm or the like to be activated.

Although a preferred embodiment of this invention has been described anddisclosed hereinbefore, it is to be remembered that variousmodifications and alternate constructions may be made thereto withoutdeparting from the true spirit and scope of the invention as defined inthe appended claims. For example, many minute changes in the position ofthe diaphragm 51 as caused by the presence of a slight negative pressurein the cavity 50, or even caused by a slight positive pressure therein,can be sensed by means substituted for the screw electrodes 32 and 33;such as a variable reluctance unit operatively connected to thecircuitry of the respirator 17, or to another device responsive toinspiration or expiration. Furthermore, in the place of the variablereluctance arrangement, variable capacitance, variable inductance, orvariable resistance arrangements could be used, as could theinterruption of a light beam as a means for sensing changes in theposition of the diaphragm.

Each of these aforementioned arrangements could be built into the plate26 for detecting minute changes in the position of the diaphragm 51, andas a means for utilizing said changes for controlled operation of therespirator 17.

We claim:

1. A pressure sensing device consisting in combination:

base plate means;

upper housing means mounted on said plate means and forming a cavitytherebetween, said cavity fluidly communicable with the atmosphere;

a diaphragm secured between said plate means and said housing means anddisposed within said cavity, wherein one side of said diaphragm isexposed to the atmosphere;

fluid means fluidly connected to said plate means for communicating afluid with said cavity on the other side of said diaphragm;

said diaphragm movably responsive to a pressure-differential betweensaid fluid means and the atmosphere;

a normally open electrical switch means having a pair of spaced contactsmounted on said plate means and extending into said cavity; and

electrically conductive disc means mounted on said diaphragm andoperable to simultaneously engage said contacts and close said switch inresponse to movement of said diaphragm;

electro magnetic means mounted on said housing means, said magneticmeans operable to control the attraction thereto of said disc meanswhereby to control the sensitivity of said diaphragm; and

screen means mounted in said cavity adjacent said one side of saiddiaphragm and interposed between said magnetic means and said diaphragm,said screen means located within said cavity such that air underatmospheric pressure is on either side of said screen means at all timesregardless of the position of said diaphragm, said screen means operableto prevent said diaphragm from engaging said magnetic means, andoperable further to allow air under atmospheric conditions to impingesubstantially the entire ex- References Cited UNITED STATES PATENTSHalbleib ZOO-83.6 Dashner et a1. 340270 Hueber et a1. 20083 Tobias200-83 10 Lusted 200-83 X CPL 6 6/1963- Horowitz 20083 10/ 1963 Caldwell128140 2/1966 Bird et a1. 128145.6 2/ 196 6 Fullman 222250 FOREIGNPATENTS 2/ 1912 Austria. 9/1896 Germany.

RICHARD A GAUDET, Primary Examiner.

K. L. HOWELL, Assistant Examiner.

